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Prevalence and causes of cough in chronic dialysis patients: a comparison between hemodialysis and peritoneal dialysis patients.

Peritoneal dialysis (PD) and hemodialysis (HD) are both common forms of dialysis for patients with end-stage renal disease. A few case reports have suggested that cough is associated with PD. From 1991 to 1998, 17 patients being treated with PD at the Toronto Western Hospital demonstrated persistent cough severe enough for referral to a respirologist. Causes of cough, often more than one cause per patient, included asthma, post-nasal drip, gastroesophageal reflux disease (GERD), chronic obstructive pulmonary disease, congestive heart failure, allergic rhinitis, pleural effusion, and respiratory infection. The aim of this cross-sectional study was to establish the prevalence of cough among PD patients, to determine if PD patients more commonly have a dry persistent cough than do HD patients, and, if the latter case is true, the possible reasons for it. A detailed survey of 92 PD patients and 91 HD patients was conducted in 1998 and 1999 at the University Health Network. Survey questions inquired about patient respiratory symptoms since onset of dialysis. Charts were reviewed to obtain information on use of medications possibly relevant to cough. In the PD and HD groups, 52% and 23% were females (p = 0.001), and the mean ages were 59.1 and 60.1 years, respectively. Angiotensin converting enzyme (ACE) inhibitors had been taken by 65% (PD) and 55% (HD) of patients, and beta-blocking medications by 43% (PD) and 51% (HD). Since initiation of dialysis--mean 2.7 years (PD) and 3.7 years (HD)--22% of PD patients reported persistent cough versus 7% of HD patients (p = 0.003). Although no significant association was seen between cough and self-reported heartburn in HD patients (p = 0.439), a significant association between cough and self-reported heartburn was seen in PD patients: 67% of PD patients with persistent cough reported heartburn versus 29% of those without cough (p = 0.008). The findings suggest that GERD and associated cough are more common in PD patients than in HD patients, perhaps owing to increases in intra-abdominal pressure from the peritoneal dialysate.

Cough↗

Cough variant asthma: usefulness of a diagnostic-therapeutic trial with prednisone.

Cough variant asthma is characterized as a persistent, nonproductive cough with minimal or no wheezing and dyspnea. The diagnosis can be overlooked or misdisagnosed. We describe the severity of cough, the misery of some patients who have this syndrome and the usefulness of a diagnostic-therapeutic trial in ten patients with cough variant asthma. We evaluated ten patients whose chief complaint was persistent nonproductive cough. During the course of evaluation, all patients received a diagnostic-therapeutic trial of prednisone for cough variant asthma after other major causes of cough had been excluded. The duration of cough ranged from 2 months to 20 years. Some patients had significant side effects from coughing including interference with social life, work and sleep, urinary incontinence, stool incontinence, hoarseness, and vomiting. After a diagnostic-therapeutic trial with prednisone, nine patients reported significant improvement of cough in three days. One patient required 2 weeks of therapy for optimal improvement. All were subsequently controlled primarily with inhaled conticosteroids. The diagnosis of cough variant asthma may not be made for a prolonged time. A short course of prednisone as a diagnostic-therapeutic trial can establish a diagnosis and be followed by an effective method of control of cough by inhaled corticosteroids.

Adolescent↗

Towards a quantitative description of asthmatic cough sounds.

This study describes a method of quantitatively characterizing cough sounds using digital signal processing techniques. Differences between asthmatic and non-asthmatic cough sounds are presented. Coughs from 12 asthmatic and 5 non-asthmatic subjects were analysed. Cough sounds and flows were digitized, at a sampling rate of 5 kHz, before and after a free-running exercise test. Individual coughs were divided into two or three phases, corresponding to the initial glottal opening burst, the quieter middle phase, and (sometimes) the final closing burst. Standard signal processing techniques were then invoked to characterize the spectral and temporal shapes of the first two phases. Factor analysis indicated that the spectral shapes of the two phases are independent, with each being largely described by the degree of "peakedness" in the spectrum, and by the balance of energy between low and high frequencies. Both the duration of the initial burst and zero-crossing rates of the cough waveform (which indicates the "spectral balance") during each of the first two phases were smaller for asthmatic than for non-asthmatic coughs. Fewer asthmatic coughs contained a final burst. Discriminant analysis between the two groups gave classification error rates of 20-30%. The peak flow recorded during the cough was significantly smaller for asthmatics, and correlated very well with the peak flow recorded during forced expiration. Thus, significant differences exist between asthmatic and non-asthmatic cough sounds. An effective representation of the temporal structure of the cough sound is required to successfully characterize the cough.

Asthma, Exercise-Induced↗

Enalapril-induced cough.

A retrospective analysis of records from an outpatient medical practice was undertaken to determine the incidence and features of cough resulting from the use of enalapril maleate. Of 209 patients taking enalapril, 22 (10.5%) required discontinuation of therapy because of an intractable, dry cough. Cough was more than twice as common in women; 16 (14.6%) of 109 women and 6 (6%) of 100 men stopped taking enalapril because of cough. The cough resolved in 21 of 22 patients within 2 weeks of discontinuation of enalapril therapy. When the patients with cough were compared with the others, there was no significant difference in age, smoking status, creatinine levels, enalapril dosage, associated cardiopulmonary disease, or concomitant administration of medications. Among the 187 study patients who did not discontinue taking enalapril because of cough, many developed a persistent, dry cough that to date has not been severe enough to require discontinuation of therapy, after a mean follow-up period of 16 months. The enalapril-induced cough is insidious, dry, persistent, benign, and reversible on discontinuation of therapy. It is important to distinguish enalapril-induced cough from cough resulting from acute illness, reactive airway disease, and congestive heart failure. Optimal clinical application of enalapril in the treatment of hypertension and congestive heart failure will require increased awareness of this incessant cough, which requires discontinuation of the therapy in about 10% of patients.

Antitussive Agents↗

Maximum voluntary cough: an indication of airway function.

Maximum voluntary coughing produces a flow-volume profile which incorporates the characteristics of a maximum expiratory flow-volume curve (MEFV). The cough flow-volume curve also has transient spikes of supramaximal flow, interspersed with portions of zero flow when the glottis is closed. The peak flow rates of the supramaximal flow transients during cough decrease in a linear fashion as lung volume goes down from total lung capacity to residual volume. Cough flow-volume curves have been recorded from forty-two subjects between the ages of 7 and 56 yr. The rate of change of cough peak flow shows a positive correlation with airway conductance measured plethysmographically in children. The ratio of forced expiratory flow to cough peak flow (the cough ratio) expresses the maximum expiratory flow rate during forced expiration as a proportion of that which can be achieved with a cough. The cough ratio declines during adult life, because although there is a fall in cough peak flow with age there is a proportionally greater fall in MEFV-equivalent flow. These investigations explore the information to be gained from cough flow-volume curves by examining the cough in a heterogeneous group of individuals.

Adolescent↗

Prevalence and repeatability of the cough response induced by inhalation of low chloride ion solutions in normal subjects.

Although the inhalation of low Cl- ion solutions has often been used to induce cough, the prevalence and repeatability of the challenge has never been studied in detail. We, therefore, examined cough response in a group of 59 volunteers (aged 15-57 yrs; 34 females and 25 males; 20 smokers) to ascertain prevalence and repeatability. Each subject performed, 2 weeks apart, two identical cough challenges by inhaling four isosmolar solutions with decreasing Cl- ion concentrations (150, 75, 37.5 and 0 mM). Each solution was delivered by a DeVilbiss 65 ultrasonic nebulizer (mean output: 1.9 mL.min-1) for 1 min, and the number of coughs was counted during the inhalation. Cough response was expressed as number of coughs.min-1. Significance of response to the cough challenge was assessed on the basis of mean number of coughs.min-1 and 95% upper confidence limit (CL) of response to the Cl- free solution in the whole population. Cough threshold for a significant response was greater than 8 coughs.min-1. Out of 59 subjects, only 20 exceeded the cough threshold (34%) after inhaling the Cl- free solution. A concentration-response effect was evident only when inhaling 37.5 and 0 mM Cl- ion solutions. A significant cough response was more likely among females (p = 0.03). Smoking did not significantly affect the prevalence of response. Coefficients of repeatability of cough response to 37.5 and 0 mM Cl- solutions in 20 responders were equal to 10.1 and 12.6, respectively. We conclude that a significant cough response to low Cl- ion solutions develops in approximately 1 out of 3 of challenged volunteers and that repeatability is not satisfactory. We suggest that cough threshold and repeatability should be preliminarily assessed, especially when the challenge is used to study the antitussive activity of drugs.

Administration, Inhalation↗

Prevalence and clinical manifestations of gastro-oesophageal reflux-associated chronic cough in the Japanese population.

Gastro-oesophageal reflux (GOR) is one of the most common causes of chronic cough in Western countries, responsible for 10 to 40% of cases. In Japan, however, GOR-associated chronic cough (GOR-CC) has been rarely reported and its clinical manifestation including frequency of concomitant reflux laryngitis is poorly known. We have analyzed prevalence and clinical characteristics of patients who were diagnosed as having GOR-CC among adult patients with chronic cough (>or= 8 weeks) who visited our asthma and cough clinic over a period of 19 months. Diagnosis of GOR-CC was based on the response of coughing to a proton-pump inhibitor (lansoprazole) and/or positive results of 24 h ambulatory esophageal pH monitoring. Laryngeal involvement was based on symptoms or objective diagnosis by specialists.GOR-associated chronic cough was diagnosed in 7.1% (8 of 112) of chronic cough patients. In addition to the demographic data which were consistent with the characteristics of patients with GOR-CC in the Western populations, including gender (6 females), age (mean +/- SE, 56.9 +/- 5.8 years), duration of cough (9.9 +/- 3.3 months), lack of gastrointestinal symptoms (3 of 8) and complication with other causes of cough (5 of 8), we found the standard range of body mass index (23.9 +/- 1.5 kg/m2) and high incidence of concomitant reflux laryngitis (5 of 8) in the present 8 patients. Among 4 patients who could stop treatment with temporal resolution of cough, cough recurred in 3 patients, 1 week to 8 months after the discontinuation. In conclusion, GOR-CC is a less frequent cause of chronic cough in Japan than in Western countries. Signs or symptoms of laryngitis may be important as clues to suspicion of GOR-CC.

Journal Article↗

Delay of diagnosis and empiric treatment of angiotensin-converting enzyme inhibitor-induced cough in office practice.

OBJECTIVE: To evaluate the length of time taken to diagnose cough due to the use of an angiotensin-converting enzyme (ACE) inhibitor and the frequency of interim diagnoses and treatments given in an office practice. DESIGN: Retrospective case study. SETTING: Two academic group family practice offices. PATIENTS: Seventeen solicited cases of patients with suspected or known ACE inhibitor-induced cough over a 2-year period. MAIN OUTCOME MEASURES: Documentation in the patient chart of the nature and complaint of the cough; the time between initiation of therapy with the drug and complaint of the cough; the time between initiation of therapy with the drug and assessment of ACE inhibitor-induced cough or discontinuation of drug treatment; other diagnoses given to explain the cough; and other treatments given. RESULTS: There was an average of 14.5 weeks between the initiation of ACE inhibitor therapy and the first documentation of the complaint of cough, and an average of 24.0 weeks between the initiation of ACE inhibitor therapy and documentation of the cough side effect. Physicians made several interim diagnoses prior to recognizing cough as a side effect of ACE inhibitor therapy. Physicians prescribed 30 medications and took two chest radiographs on seven patients experiencing ACE inhibitor-induced cough prior to recognition of this side effect. CONCLUSIONS: The investigation found a significant delay in making the final diagnosis of ACE inhibitor-induced cough. Frequently, physicians gave other diagnoses, ordered unnecessary diagnostic tests, and ordered treatments other than the discontinuation of ACE inhibitor therapy. Earlier identification would be more cost-effective.

Aged↗

Impact of chronic cough on quality of life.

BACKGROUND: Cough is the most common complaint for which adult patients seek medical care in the United States; however, the reason(s) for this is unknown. OBJECTIVES: To determine whether chronic cough was associated with adverse psychosocial or physical effects on the quality of life and whether the elimination of chronic cough with specific therapy improved these adverse effects. METHODS: The study design was a prospective before-and-after intervention trial with patients serving as their own controls. Study subjects were a convenience sample of 39 consecutive and unselected adult patients referred for evaluation and management of a chronic, persistently troublesome cough. Baseline data were available for 39 patients and follow-up for 28 patients (22 women and 6 men). At baseline, demographic, Adverse Cough Outcome Survey (ACOS), and Sickness Impact Profile (SIP) data were collected and patients were managed according to a validated, systematic protocol. Following specific therapy for cough, ACOS and SIP instruments were readministered. RESULTS: The ages, sex, duration, and spectra and frequencies of the causes of cough were similar to multiple other studies. At baseline, patients reported a mean +/- SD of 8.6 +/- 4.8 types of adverse occurrences related to cough. There were significant correlations between multiple ACOS items and total, physical, and psychosocial SIP scores. Psychosocial score correlated with total number of symptoms (P<.02). After cough disappeared with treatment, ACOS complaints decreased to a mean +/- SD of 1.9 +/- 3.2 (P<.0001) as did total (mean +/- SD, 4.8 +/- 4.5 to 1.8 +/- 2.2) (P= .004), psychosocial (mean +/- SD, 4.2 +/- 6.8 to 0.8 +/- 2.3) (P = .004), and physical (mean +/- SD, 2.2 +/- 2.9 to 0.9 +/- 1.8) (P = .05) SIP scores. Multiple linear regression analysis showed that 54% of variability of the psychosocial SIP score was explained by 4 ACOS items while none of the physical score was explained. CONCLUSIONS: Chronic cough was associated with deterioration in patients' quality of life. The health-related dysfunction was most likely psychosocial. The ACOS and SIP appear to be valid tools in assessing the impact of chronic cough.

Chronic Disease↗

Inhaled corticosteroids for non-specific chronic cough in children.

BACKGROUND: Cough in isolation of other clinical features is known as non-specific cough, which has been defined as non-productive cough in the absence of identifiable respiratory disease or any known aetiology. In children with non-specific cough the possibility of asthma being the underlying disorder is often raised (so called cough variant asthma). The proponents of cough variant asthma suggest a therapeutic trial of medications usually used to treat asthma. OBJECTIVES: To determine the efficacy of inhaled corticosteroids in non-specific cough in children over the age of two years. SEARCH STRATEGY: Searches were conducted on Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE. Searches were current as of March 2004. SELECTION CRITERIA: All randomised (randomised and quasi-randomised) controlled clinical trials in which an inhaled corticosteroid (beclomethasone (BDP), fluticasone (FP), triamcinalone (TAA) or any other corticosteroid) were given for cough in children over two years of age were included. Two review authors independently assessed articles for inclusion and methodological quality. DATA COLLECTION AND ANALYSIS: Data from trials was extracted by both review authors and entered into the Cochrane Collaboration software program RevMan Analyses 1.0.2. MAIN RESULTS: Two trials met the inclusion criteria (123 participants). One compared inhaled beclomethasone dipropionate (400 micrograms per day) with placebo and the other compared fluticasone propionate (2 mg per day for 3 days followed by 1 mg per day for 11 days) with placebo. Both studies used metered dose inhalers via a spacer. With the lower dose of inhaled corticosteroid there was no significant difference between the beclomethasone and placebo groups. With the higher dose there was a significant improvement in nocturnal cough frequency after two weeks in children presenting with persistent nocturnal cough. However, a significant but smaller improvement was also seen with placebo. AUTHORS' CONCLUSIONS: In one study beclomethasone dipropionate (400 micrograms per day) was no different from placebo in reducing the frequency of cough measured objectively or scored subjectively. There might be a small improvement with very high-dose inhaled corticosteroid but the clinical impact of this is unlikely to beneficial.

Adrenal Cortex Hormones↗

Correlation between cough frequency and airway inflammation in children with primary ciliary dyskinesia.

Cough is common in airway disease. We measured cough frequency in children with primary ciliary dyskinesia (PCD), to determine how accurately families assess this symptom; and to assess the relationship between cough frequency and airway inflammation, measured using induced sputum and exhaled nitric oxide (eNO). Twenty stable PCD children (7 boys), median age 10.8 years (interquartile range (IQR), 9-14), and 10 healthy control children, median age 12 years (IQR, 10.5-12.7), were recruited. ENO was measured using a chemiluminescence analyzer, with sputum induction with 3.5% saline. PCD children underwent ambulatory cough monitoring. Sputum neutrophils were higher in PCD (median, 70.3%; IQR, 55.3-78%) compared to controls (median, 27%; IQR, 24.5-33%; P = 0.004); cough frequency was higher (median episodes, 19; IQR, 11-22.5) compared to healthy children (median episodes, 6.7; IQR, 4.1-10.5; P < 0.001). Forced expiratory volume in 1 sec (FEV(1) percent predicted) and eNO were lower in PCD (median, 63%; IQR, 57-85%; P < 0.0001); eNO (median, 7.1 ppb (IQR, 4.8-19.1 ppb) vs. 12.4 ppb (IQR, 10.3-17.3 ppb), P = 0.043). Parental scoring of day and night cough correlated with recorded cough (r = 0.930, P < 0.0001, daytime; r = 0.711 for nighttime, P = 0.002). Visual analogue score and cough episodes also correlated positively (r = 0.906; P < 0.0001). There was a positive correlation between cough frequency and sputum neutrophil count in PCD (Spearman's r = 0.693, P < 0.002), but not percent FEV(1) or eNO. Stable PCD children have increased cough frequency and neutrophilic airway inflammation. In conclusion, cough frequency correlated with sputum neutrophils but not with FEV1 or eNO.

Adolescent↗

Tachyphylaxis to capsaicin-induced cough and its reversal by indomethacin, in patients with the sinobronchial syndrome.

Cough reflex testing with capsaicin has been used to study the pathophysiology of the cough reflex and the antitussive effects of various drugs. Although the reproducibility of capsaicin-induced cough has been well established in normal subjects, it is not known if prior challenge with capsaicin reduces the subsequent cough response to inhaled capsaicin in patients with the sinobronchial syndrome, a condition characterized by chronic upper and lower airway inflammation. Measurement of the capsaicin cough threshold, defined as the lowest concentration of capsaicin eliciting five or more coughs, was repeated four times at intervals of 15, 30 and 60 min in eleven patients with the SBS and ten normal subjects. The cough thresholds at 15, 30 and 60 min were greater than the initial value in patients with the SBS but not in normal subjects. In addition, we examined the effect of 4 days treatment with indomethacin (100 mg/day) on the cough thresholds measured twice at an interval of 15 min in eight patients with the SBS. Indomethacin increased the initial cough threshold and reduced the increment in the post-15 min cough threshold from the initial value compared with placebo, thus reducing the tachyphylaxis. These results indicate that chronic airway inflammation may be responsible for the decreased response (tachyphylaxis) to repeated inhalation of capsaicin, and suggest that cyclooxygenase products released by the airway inflammation may be involved in tachyphylaxis, cough receptor sensitivity to inhaled capsaicin, or both, in patients with the SBS.

Adult↗

Effect of codeine on the inspiratory and expiratory burst pattern during fictive cough in cats.

Experiments were conducted to study the effect of the opioid, codeine, on different components of the cough motor pattern. Midcollicular decerebrate cats were paralyzed and artificially ventilated by a pump triggered by the phrenic neurogram. Inspiratory (phrenic) and expiratory (cranial iliohypogastric) neurograms were recorded. Fictive cough was produced by mechanical stimuli applied to the intrathoracic trachea. Codeine (0.03-1.0 mg.kg-1, i.v.) decreased cough frequency (average number of coughs per stimulus trial), expiratory burst amplitude, and inspiratory burst amplitude in a dose-dependent manner. The maximum reduction in cough frequency and expiratory amplitude produced by codeine was 80-90% for both parameters. However, codeine was more potent in reducing cough frequency (ED50 = 0.1 mg.kg-1) than expiratory burst amplitude (ED50 = 0.35 mg.kg-1). The maximum observed reduction of inspiratory burst amplitude elicited by codeine was approximately 40%. There was a positive linear relationship between phrenic and cranial iliohypogastric burst amplitudes during fictive cough (r = 0.82, P < 0.001). Codeine destabilized the motor pattern during fictive cough by disrupting this relationship between inspiratory and expiratory burst amplitudes. We conclude: (a) the central pattern generator for cough is functionally organized into a cough frequency generator, an expiratory burst amplitude generator and an inspiratory burst amplitude generator, each of which have different sensitivities to codeine (b) there exists a specific codeine-sensitive neural mechanism matching the relative magnitude of central drive to inspiratory and expiratory motoneurons during cough.

Animals↗

Involvement of P2X receptor subtypes in ATP-induced enhancement of the cough reflex sensitivity.

We examined the effect of inhaled ATP on the chemical irritant-induced coughs to clarify the roles of ionotropic purinergic receptors in these modulations. Although inhalation of 0.1 M citric acid by itself produced only a few coughs in guinea pigs, exposure to ATP, at concentrations of 3-10 microM, for 2 min concentration-dependently increased the number of 0.1 M citric acid-induced coughs. ATP-induced enhancement of the number of citric acid-induced coughs was abolished when animals were pretreated with 2',3'-O-(2,4,6-trinitrophenyl) adenosine 5-triphosphate (TNP-ATP), an antagonist of P2X receptor subtypes P2X1-4, at a concentration of 50 microM, for 2 min. However, exposure to pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), an antagonist of P2X receptor subtypes P2X1,2,3,5,7, but not of P2X4 receptors, at a concentration of 50 microM, for 2 min, had no effect on the ATP-induced enhancement of the number of citric acid-induced coughs. Furthermore, exposure to reactive blue 2 (RB2, 30 microM, 2 min), an antagonist of P2Y receptors, had no effect on the ATP-induced enhancement of the number of citric acid-induced coughs. Exposure to ATP, at a concentration of 10 microM, for 2 min significantly increased the number of citric acid-induced coughs in capsaicin-pretreated guinea pigs. Furthermore, ATP had no effect on the number of capsaicin-induced coughs in naive animals. These results suggest that although ATP, by itself, does not elicit spontaneous coughs, it likely enhances the cough reflex sensitivity. Furthermore, stimulation of P2X receptors, especially P2X4 receptors, on rapidly adapting receptors may be required for the ATP-induced enhancement of the cough reflex sensitivity.

Adenosine Triphosphate↗

Cough as a symptom.

The Third International Symposium on Cough focused on acute and chronic cough, both clinical and basic science. Cough is a defensive and clearing mechanism, and can cause discomfort and nuisance; it is also an important symptom of many chronic airway diseases. In this Symposium, several issues concerning the relationship of cough to disease processes, different types of cough, and the concept of idiopathic cough will be discussed. Characterization of cough receptor(s) and identification of peripheral and central mechanisms for cough sensitization are current areas of investigation for delineating the cause of chronic cough. Peripheral mechanisms may be most important for acute cough such as after viral infections. The role of pathological changes at the level of the airway mucosa and of cortical pathways will be reviewed. Finally, therapeutic inhibition of the cough reflex remains an area of active research.

Cough↗

Modulation of experimentally-induced cough by stimulation of nasal mucosa in cats and guinea pigs.

Stimulation of afferent nerves in upper airways may contribute to the pathogenesis of chronic cough in chronic disorders of nose and/or sinuses. We tested the hypothesis that stimulation of the nasal afferent nerves enhances experimentally-induced cough. Intranasal administration of capsaicin (50 microM, 25 microl) did not evoke cough in anaesthetized cats, but enhanced cough induced by mechanical stimulation of the tracheobronchial mucosa (number of coughs, median [IQR]) (6.5 [5.5-8.5] versus 10 [7-14]; P = 0.028, n = 13). In contrast, intranasal histamine (16 mM, 25 microl) had no effect. Intranasal capsaicin (50 microM, 15 microl) did not evoke cough, but enhanced cough evoked by mechanical stimulation of the tracheobronchial mucosa (1 [1-3] versus 3 [2-4]; P = 0.0037, n = 15) in anaesthetized guinea pigs and cough induced by inhalation of citric acid (0.3M, 2 min) in awake guinea pigs (3 [2-5] versus 5 [3-7], P ? 0.0026, n = 23). We conclude that stimulation of nasal afferent nerves with capsaicin enhances experimentally-induced cough. Our results suggest that afferent inputs from the nose interact with the cough reflex pathways in a manner that enhances cough.

Animals↗

Cough and ventilatory adjustments evoked by aerosolised capsaicin and distilled water (fog) in man.

Airway receptors mediate cough and ventilatory adjustments. Simultaneous assessment of cough sensory-motor components and changes in breathing pattern may provide insights into the receptor(s) prevailingly stimulated by inhaled irritants. Nineteen subjects inhaled capsaicin and fog up to threshold concentrations for cough. Cough intensity, respiratory sensations and changes in breathing pattern induced by the two irritants were compared. Capsaicin and fog cough threshold values did not correlate. Coughing induced by both agents was preceded by qualitatively similar sensations and by significant increases in minute ventilation and respiratory drive due to selective increases in tidal volume (P<0.01). Cough intensity was similar with both agents. Cough frequency and the intensity of the urge to cough were higher with capsaicin (P<0.01). The lack of correlation between fog and capsaicin cough threshold values suggests differences in the neural mechanisms activated. The selective increase in tidal volume suggests prevailing involvement of rapidly adapting receptors. The stronger sensations evoked by capsaicin may contribute to the higher cough frequency observed with this agent.

Adult↗

The relation of rhinitis to recurrent cough and wheezing: a longitudinal study.

BACKGROUND: Recurrent cough can be a clinical manifestation of rhinitis. However, it remains unclear if the association between rhinitis and recurrent cough among children is independent of asthma. OBJECTIVE: The aim of the present study was to determine, in a large longitudinal cohort, whether rhinitis is significantly associated with recurrent cough alone, wheezing alone, or the combination of both symptoms during childhood. METHODS: We investigated determinants of recurrent cough, with or without wheezing, using longitudinal data from the Tucson Children's Respiratory Study. Among the 1246 subjects originally enrolled, 1024 children completed at least one questionnaire between the ages of 6 and 18 years and were included in the present study. In any survey, wheezing was defined as at least one wheezing episode during the past year and recurrent cough as two or more coughing episodes lasting at least 1 week without a cold during the past year. Generalized estimating equations were used to determine significant risk factors. RESULTS: After adjusting for sex, skin test reactivity and parental asthma, both rhinitis (OR = 2.47 CI = 1.84, 3.30) and sinusitis (OR = 1.54 CI = 1.11, 2.14) were associated with an increased risk of recurrent cough plus wheezing. The OR associated with rhinitis were significantly reduced for subjects reporting only recurrent cough or only wheezing (OR = 1.43, CI = 1.03, 1.99; and OR = 1.30, CI = 1.07, 1.58, respectively). Recurrent cough and wheezing, when examined independently, showed different patterns of risk factors. CONCLUSION: We found rhinitis to be an independent risk factor for both recurrent cough and wheezing during childhood. Different pathways may be involved in the association of rhinitis with recurrent cough and wheezing.

Adolescent↗